Adaptive optic wafer stepper illumination system

A stepper illuminating system for manipulating focus and aberrations in optical wavefronts and for projecting a pattern of a reticle onto a wafer comprising:

• a light source to project light through said reticle;
• a beamsplitter disposed between said patterned reticle and said deformable mirror to reflect a portion of the incident light and a portion of light reflected by said wafer;
• a deformable mirror to redirect said light projected through said reticle, said deformable mirror having a reflective surface on a front side and a plurality of distortive actuators on a backside, each of said plurality of distortive actuators being capable of selectively distorting the reflective surface upon application of electrical signals to at least one of said actuators;
• a secondary mirror to receive the redirected light from said deformable mirror and expand and reflect the redirect light;
• and
• a primary mirror to receive the redirected light from said secondary mirror and reduce and focus the redirected light onto said wafer so that a reduction of said pattern of said reticle is projected onto said wafer;
• whereby said focus and said aberrations of said optical wavefronts in the redirected light are manipulated by selected deformation of said deformable mirror.

A method for manipulating focus and aberrations in optical wavefronts in a stepper illumination system for projecting a reduced pattern of a patterned reticle onto a wafer which comprises:

• selecting a light source which emits light within the deep ultraviolet spectrum;
• projecting light from said light source through said patterned reticle;
• redirecting the light projected through said reticle with a deformable mirror toward a secondary mirror;
• expanding and reflecting toward a primary mirror the redirected light with said secondary mirror;
• focusing the redirected light onto said wafer with said primary mirror whereby said reduced pattern is projected onto said wafer;
• reflecting a portion of the redirected light from said wafer;
• using said reflected portion to determine focusing errors and aberrations;
• and
• selectively deforming said deformable mirror to manipulate said focus and aberrations.

A method for realtime manipulation of focus and aberrations in optical wavefronts in a stepper illumination system for projecting a pattern from a patterned reticle onto a wafer which comprises:

• inserting a deformable mirror within a light path of said illumination system downstream from said patterned reticle;
• inserting a beamsplitter between said patterned reticle and said deformable mirror for diverting a portion of incoming light and a portion of light reflected from said wafer toward a detector;
• generating an interference pattern corresponding to said focusing errors and said aberrations by combining both said portions of light;
• detecting said interference pattern;
• and
• converting said interference pattern into an electrical signal for controlling said deformable mirror.